Ezjail is fairly old. It works with the older less capable API to jails and is restricted to features supported by the old API. It was also designed for use with UFS on tiny disks.
Lets say you are a webhoster around the year 2000 and your servers have a handfull 36GB or 72GB SCSI disks. You want to protect each customer from all other customers and protect yourself from all customer scripts. This was before IA32 CPUs offered the features to support efficient transparent virtualisation and even if they did the resource demand per VM would have been too high. As long as your customers are happy with static file hosting everything is fine, but as soon as way want to execute some useful server side scripts you have a problem. FreeBSD offers a way to run one HTTP server per customer inside jail, but keeping a full FreeBSD userland (base + http server + databases + scripting language + customer code) per customer would quickly fill your puny little disks. Ezjails offers a neat solution to the problem: store a template just once and instantiate it with a nullfs read-only mount. Now your storage requirements are manageable at a reasonable price with hardware of the day and your buffer cache hitrates are better too. All of these indirection and aliasing hacks make ezjail more complicated than modern jail managers, because ezjail had to work around the operating system limitations instead of taking advantage yet to be invented operation system features.
Sharing one basejail via nullfs is useful feature, can Iocage do this?
Nullfs not only allows to save space on disk but also allows faster updates (extract new basejail then switch all jails to it, without full upgrade of each jail).
Also in software old doesn't mean bad, and newer is not automatically better.
I didn't mean to imply that. I just explained why ezjail looks so convoluted to a new user. Ezjail still solves the same problems today as it did 10 years ago. On the other hand since not even bloatware did keep up with storage cost decreases users can afford more comfortable trade-offs today.
I've found iocage's user interface to be more intuitive. I started using iocage because ezjail broke something when trying to upgrade a jail, but that was probably me doing something wrong.
Lets say you are a webhoster around the year 2000 and your servers have a handfull 36GB or 72GB SCSI disks. You want to protect each customer from all other customers and protect yourself from all customer scripts. This was before IA32 CPUs offered the features to support efficient transparent virtualisation and even if they did the resource demand per VM would have been too high. As long as your customers are happy with static file hosting everything is fine, but as soon as way want to execute some useful server side scripts you have a problem. FreeBSD offers a way to run one HTTP server per customer inside jail, but keeping a full FreeBSD userland (base + http server + databases + scripting language + customer code) per customer would quickly fill your puny little disks. Ezjails offers a neat solution to the problem: store a template just once and instantiate it with a nullfs read-only mount. Now your storage requirements are manageable at a reasonable price with hardware of the day and your buffer cache hitrates are better too. All of these indirection and aliasing hacks make ezjail more complicated than modern jail managers, because ezjail had to work around the operating system limitations instead of taking advantage yet to be invented operation system features.